Commutator construction



April 24, 1951 c. LYNN COMMUTATOR CONSTRUCTION Filed Jan. 10, 1950INVENTOR Cldrence Lynn. avra & e

ATTORNEY Patented Apr. 24, 1951 COMMUTATOR CONSTRUCTION Clarence Lynn,Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application January 10,1950, Serial No. 137,'710 6 Claims. (ol. 171 321) My invention relatesto commutator-type rotormembers of dynamo-electric machines, and it hasparticular relation to the kind of commutators which are used inhigh-speed, direct-driven, turbo-generator exciters.

In commutator-constructions of the type to which my invention relates,the commutatornecks are thinner, circumferentially, than the commutatorbars. In order to prevent dirt-laden air from passing back through thespaces between the commutator-necks, and depositing a layer ofelectrically oonducting dirt underneath the coil-ends of thearmature-winding, and ultimately providing a short-circuiting path ofrelatively high resistance to ground, it has been customary to fill thespace under the coil-ends, between the commutator-necks and the frontend of the rotor-core, and also the circumferential spaces between thecommutator-nccks, with a heat-hardening asbestos filling-compound orcement. This expeclient has been practiced for some time, because of theurgency of the necessity for preventing conducting deposits from formingback of the commutator-necks, notwithstanding the fact that it hasresulted in a considerable increase in the temperature of thecommutator. In some cases, this has presented a considerable problem inkeeping the temperature-rise to the guaranteed 55 at ratedloadconditions i It is an. object of my present invention to overcomethe excessive-temperature difficulty by filling only the back portionsof the circumferential spaces between the commutator-necks, leavingsubstantially large unfilled spaces between the front porticns of theoommutator-necks, thus causing said front portions of the necks to actas fan-blades and as heat-radiatng surfaces for conducting heat awayfrom the commutator-bars. In one instance, this expedient has resultedin as much as an l8 reduction in the commutatortemperature. In thehigh-speed machines to which my invention is more particularlyapplicable, it is necessary or desirable to use banding around thecommutator-nccks, in order to restrain them against centriiugal force,and when my present invention is used, this banding is applied only overthe filled rear portions of the commutator-necks Incommutator-constructions of the type having solid necks, or necks whichare thick in a circumierential direction, so that there is substantiallyno space between adj acent necks, it has been custcmary, heretofore, touse a filling-cement or compound back of the necks, and underneath thecoil-ends of the armature-winding, butthese constructions have lackedthe spaced thin front neck-portions which act as fan-blades andheat-dissipating surfaces in accordance with my invention.

With the foregoing and other objects in view,

my invention consists in the structures, combi-.

nations, parts, and methods of design and operation, hereinafterdescribed, claimed and illustrated in the accompanying drawing, wherein:

Figure 1 is a fragmentary longitudinal section of a portion of adynamo-electrc machine, illustrating my invention, the section-planebeing indicated by the broken line I-I in Fig. 3;

Fig. 2 is a fragmentary transverse sectional View along the line II-IIin Fig. 1, with a portion of the figure broken back to show a sectionalong the line IIa-IIa of Fig. 2, and

Fig. 3 is a ragmentary cylindrical section on the line III- III of Figs.1 and 2.

I show my invention applied to a dynamo-electrio machine having astator-member I and a' rotor-member 2. The rotor 2 has a core 3 mountedon a shaft 4. spaced axially from the e front end of the rotor-core, isa commutator',

which is illustrated as comprising a plurality of commutator-bars 6 andmica bars 6' (Figs. 2 and 3), which are held in place by a shrink-ring T(Fig. 1), which is centered and supported within a centering-plate 8.The centering-plate 8 is supported on a commutator-bush or shell 9,which is mounted on the shaft 4, in accordance with a knownConstruction. The centerng-plate 8 also has a portion extending radiallyoutwardly far enough to constitute a coil-support o.

The commutator 5 is also provided with a plurality of commutator-necksIG which are thinner, circumferentially, than the bars 6, saidcommutator-necks being set into, and securely fastened within, suitablesaw-outs IT (Figs. 1 and 2) a in the respective bars, in accordance witha known mutator-necks 16 and the front end of the rotorcore, construingthe insulating-pad 23 and the centering-plate 8 (when used) asconstituting the front end of the core-Construction 3. 'I'he idea is, tofill the space underneath the coil-ends l8, so that no conductingdeposit may be carried there by the ventilating-air. The insulating pad23 is used between the two layers of the front end-windings of thearmature, in the case of a two-layer armature-winding.

In the particular illustrated form of my invention which is shown in thedrawing, I preferably use a plurality of neck-wedges 22 which are madeof solid insulating material, and which are disposed between the rearportions of the circumferential spaces between the commutatornecks 16,thus leaving substantially large unfilled spaces 24 between the frontportions of the commutator-necks. In the particular form of embodimentwhich is shown in the drawing, the coil-ends |8 are disposed at one sideof the respective necks l6 to which they are attached, and therespective neck-wedges 22 are disposed between the other sides of thesecoil-ends !8, and the other side of the next adjacent'neck 15, leavingspaces 25, under the coil-ends 58. These spaces 25 are also filled withcement 2l.

In operation, the essential feature of my invention is that the necksIS' shall be 'thinner, circumferentially, than the commutator-bars E, sothat there is a circumferential spacing between successive necks. Therear halves, orother suitable portion, of this between-neck spacing isfilled' by a suitable filling, which is generically indicated at 28 inthe drawing, and which may consist of cement alone, or suitably fittedneckwedges alone, or, :as shown, partly cement and partly theneck-wedges. It is important that the front spaces 24' should be leftunfilled, occupying the front half-inch, or other substantially largeportion, of the' spaces between the successive necks.

In the particular form of invention which is illustrated in' thedrawing, the neck-wedges 22 are wide enough, in an axial direction, toextend backwardly for about a quarter of an inch behind the rear ends ofthe eommutator-necks IS, and these rearwardly extendingportions of 'thewedges 22 are provided with vertical grooves 26, 01' other 'means forproviding shoulders 21 (Fig. 3) for `interlocking engagement with thefilling-compound 2|, so that the filling-compound helps to hold thewedges'in place.

When my invention is applied to high-speed machines, such asturbo-exciters, it is necessary, or quite desirable, to use banding 28,both over the coiI-ends IS, and over the rear filled portions of thespaces between the commutator-necks !6, but this banding should noteXtend over the front unfilled spaces 24`between the necks. The bandingthus serves to retain both the necks !5, and the neck-we'dges 22,against centrifugal force. At the same time, the banding does not extendforward far enough to interfere with the radial air-flow which isinduced by the spaced front halves of the necks l 6.

Experience has shown that my invention results in just as goodprevention of short-circuiting deposits by the dustand dirt-ladenventilatingair, as in the previously used constructions. The bandingwhich extends over the rear halves of the necks adequately retains thenecks against centrifugal force, and when my neek-wedges 22 are used,this banding also adequately retains the wedges against centrifugalforce. At the same time, the omission of the banding over the unfilledfront spaces 24 between the commutatornecks, leaves an unimpeded pathfor the free radial blast of ventilating-air, which is produced by thefan-blade action of the front halves of the necks. In one particularinstance, the introduction of my invention produced a commutator havinga temperature-rise of 43 C., which is 12 below the usual guarantee,whereas, with the old form of Construction, without the unfilledsubstantially large front spaces 24, the temperaturerise was 61, or 6over the guaranteed temperature-rise.

While I have illustrated and `described my invention in a single form ofembodiment, which is at present preferred, it will be obvious that myinvention is susceptible of considerable Variation, by way of additions,omissions and the substitution of equivalents, without departing fromthe essential 'spirit of the invention. I desire, therefore, that theappended claims shall be accorded the broadest Construction consistentwith their language.

I claim as my invention:

1. A commutator-type dynamo-electric machine having a rotor-core, anarmature-winding carried by the rotor-core, a commutator spaced axiallyfrom the front end of the rotor-core, said commutator comprising aplurality of commutator-bars, and commutator-necks which are thinner,circum'ferentially, than the bars, said commutator-ne'cks being setinto, and securely fastened to, the respective bars, electricalconnections'between the commutator-necks and the coilends of thearmature-winding, and a filling including a hardenable insulatngfilling-compound, said filling occupying the space under the coilends,between the commutator-necks and the front end of the rotor-core, andalso filling the rear portions of the circumferential spaces between thecommutator-necks, leaving substantially large unfilled spaces betweenthe front portions of the commutator-necks.

2. The invention as defined in claim 1, characterized by said fillingcomprising also solid neckwedges disposed between said rear portions ofthe commutator-necks.

3. The invention as defined in claim 1, characterized by said fillingcomprising solid neckwedges disposed between said rear portions of thecommutator-necks, said neck-wedges extending to the rear of said=commutator-necks and having shoulder-portions for interlockingengagement with said 'filling-compound.

4. The invention asdefined in claim 1, in combinaton with banding aroundsaid coil-ends and around said filled portions, but not around theunfilled portions, of the commutator-necks.

5a The invention as defined in claim 1, in combination with bandingaround said coil-ends and around-said filled portions, but not aroundthe unfilled portions, of the commutator-necks, said filling comprisingalso solid neck-wedges disposed between said rear portions of thecommutator-necks.

G. The invention as defined in claim 1, in combination with bandingaroundsaid coil-ends and around said filled portions, but not around theunfilled portions, of the commutator-necks, said filling comprisingsolid neck-wedges disposed between said rear portions of thecommutatornecks, said neck-wedges extending to the rear of saidcommutator-necks and having shoulderportions for interlocking engagementwith said filling-compound. I

CLARENCE LYNN BEFERENCES CITED UNITED STATES PATENTS Name Date EdisonOct. 20, 1885 Number

